The present invention has its most important application in annotatable archival recording systems employing an intermediate film strip carried by a movable film head having supply and takeup reels for the film strip and which is moved between an imaging station and an image transfer station under conditions where bowing stresses are applied to the selected areas of film strip to be imaged at one or more of these stations.
There has been developed by the applicants and co-workers an archival hard copy microfiche recording system which reflects light off of a document placed on a document-receiving platform and projects an image of it in greatly reduced form onto an initially transparent intermediate dry silver film strip carried by a film head unit. The film strip is dispensed from a cassette mounted on the film head, and is fed by film advancing means to an imaging region where a selected area of the film strip to be exposed can receive the projected light image. A pressure element presses the selected area of the film strip against a planar backing aperture defining a projection plane and an imaging area, and the film is then exposed to the light image. The film head is next moved along guides from the imaging station to a developing station, where a hot shoe pressing against the exposed area of the film causes development of the image to form an opaque image in the exposed areas thereof. The film head is then moved to an image transfer station, where the image on the dry silver film is to be replicated on a positive initially opaque microfiche film card of the photo-developing type (See U.S. Pat. No. 4,137,078 issued June 30, 1979 to Izu and Ovshinsky). The microfiche card is held indexed on a movable carriage so that a predesignated frame of the card receives the image on the intermediate film. A pressure element presses the film card and the intermediate film strip together between the output prism of a flash lamp housing and a backing plate. Image transfer is accomplished by energizing the flash lamp to direct light through the intermediate film, immediately rendering transparent the previously opaque areas struck by the high intensity flash lamp light on the selected frame of the microfiche film card. To replicate a new image the film head is returned to the imaging station, where the cycle is repeated.
The bowing stresses applied to the intermediate film during the foregoing processes may cause erratic shifting of the film, resulting in a lack of proper image positioning on the microfiche film card and in some cases image destruction. The intermediate film is typically subjected to bowing stress during both the development and image transfer operations, and is thus vulnerable to such shifting. The prior art discloses neither a recognition of this problem in traveling film head systems nor a remedy for it. The closest prior art is disclosed in U.S. Pat. No. 4,123,157, issued Oct. 31, 1978 to Klose and Ovshinsky. The system disclosed therein uses an intermediate film strip advanced by a takeup motor and tensioned by a slip brake, and discloses no provision for retaining accurate image centering.
The microfiche card may be examined via a "read" mode of the system. With the cassette carriage positioned away from the imaging lens, the microfiche film card carriage, which is accurately locatable in x and y directions by means of an indexing system, is moved on a track to a station under the lens. An illumination system is moved next to the microfiche film card carriage, and then the chosen frame of the card is projected back to the document receiving area. No severe film shifting problems are encountered in carrying out simple "record" and "read" operation. Only a major shift of the intermediate film may cause loss of record.
The system also possesses the capability of "annotating" or "updating" existing records stored on the microfiche film. This arises from the nature of the two film systems used. The intermediate film is of the reversal type; dark areas on the chosen hard copy replicate as transparent areas and light areas replicate as opaque upon development. Hard copy having black lettering on a white page will thus replicate on the intermediate film as an opaque rectangle with transparent letters. The microfiche film, however, is an initially opaque photodeveloping positive film which is rendered irreversibly transparent where struck by high intensity light during flash exposure. Thus, dark markings on the original document replicate as irreversibly transparent images on an otherwise still opaque microfiche film frame. These remaining opaque regions on the microfiche film remain "annotatable", i.e. convertible in that they can be rendered transparent by a subsequent flash exposure. It is this aspect of the microfiche film that allows for updating of microfiche records. As used throughout this disclosure and in the appended claims the term "annotatable" will be understood to refer to a film that is capable of accepting a second image after exposure and development of a first image in the same general region.
Thus, if a copy of a document is imaged on a microfiche film card frame where the indicia on the document are dark lines on a light background, these dark lines are now stored as irreversible clear lines on the microfiche film card. To update the microfiche film card with new entries in a specified still convertible area of a microfiche film card frame one prepares on intermediate film a fresh image consisting of the new entries only. This is accomplished by using as a source for the new image a dark-line record on a white background placed on the document receiving platform, e.g. typewritten black text on white paper. The new image, consisting after development solely of transparent new entries on an otherwise opaque imaging area, is then replicated at the transfer station onto the microfiche film card frame. These new entries are thus replicated as additional irreversible clear indicia on the selected frame. Proper registry of the new record is achieved by using the "read" mode of the system to assist in orienting the new entries on the document receiving platform before the intermediate film is exposed to receive the new image. Here an image of the chosen frame to be updated is projected back onto the document receiving platform, using the "read" mode previously described. A white sheet of paper bearing the new record indicia is then placed on the document receiving platform and moved around until the new indicia are properly positioned with respect to the projected image of the microfiche film card. The frame is now updated by carrying out a conventional "record" cycle, i.e. the microfiche film card is returned to the transfer station, the film head is moved to the imaging station, whereupon the image of the new record indicia is projected, exposed, developed, and replicated onto the microfiche film card frame at the transfer station. Here even a minor erratic image shift from exposure to transfer can become of major importance, e.g. a bookkeeping update entry prints onto the wrong line or column. Also, if the bowing stress should shift the transparent unimaged margin of the intermediate film adjacent the imaged area into the projection field at the transfer station this can obliterate the previous record along a narrow band at the side of the microfiche film card frame, which receives the unwanted band of flash flamp light through the transparent portion of the intermediate film undesirably shifted into this field. It thus becomes essential that the intermediate film be prevented from undergoing significant erratic shift during its movement between the imaging and transfer stations. In practice, this latter condition is difficult to fulfill. One of the objects of this invention is to hold the erratic movement of the intermediate film to a harmless minimum without risk of damage to the film under the bowing stresses involved.
It is clear that a break in the intermediate film can cause complete wipe-out of the microfiche image during annotation because then the entire flash lamp projection field strikes the previously imaged frame of the microfiche film card exposed for annotation, and so all areas of the exposed frame are made transparent, obliterating the image thereon. Hence, another object of this invention is to achieve protection from such an occurrence.
The end-of-film condition acts like a "film break" situation and obviously occurs frequently as each roll of intermediate film is used up, and so a special additional sensing system for this condition is desirable. Another object of this invention is to make special provision to sense an imminent end-of-film situation and guard against record loss therefrom.